There is conventionally proposed an apparatus using a lateral distance sensor that transmits search waves towards a lateral region relative to the vehicle mounted with the apparatus and receives reflected waves reflected by an object existing in a propagation range of the search waves, thereby detecting a distance to the object existing in the lateral region.
For instance, Patent literature 1 discloses an apparatus that detects an obstacle using a lateral distance sensor, stores a relative position of the detected obstacle against the vehicle, and issues an alarm when the distance between the vehicle and the relative position of the obstacle is equal to or less than a predetermined distance.